Printed wiring boards are known which have a core made of organic insulating materials (e.g., fiberglass reinforced epoxy resin), and even those where the core is of metallic material. Of these boards, a board whose core is made of metal, especially an effective heat conductor such as aluminum, is excellent in heat radiation, mechanical strength, etc. and is suitable for high density packaging. A known metal cored board having a core made of aluminum (Al), as disclosed in, for example, Japanese Published Unexamined Patent Applications (PUPAs) No. 61-131552, No. 62-132392, and No. 63-98179, generally has such construction that an organic, non-conductive layer is formed over the aluminum core and a wiring layer is formed over the organic non-conductive layer. It is assumed that aluminum oxide is usually formed over the surface of the aluminum core.
In such known constructions, since the adhesive force between the aluminum core and the organic non-conductive layer is insufficient, the organic non-conductive layer may become separated from the aluminum core, particularly in an environment of high temperature and high humidity. Further, in such known constructions, when copper plating for a conductive path is provided on the inner surface of a pierced bore (for a through hole) formed in the aluminum core, a problem results wherein the aluminum core is eroded by a strong alkali solution typically used in the process of copper plating. Still further, one structure in JA PUPA No. 62-48089 shows a metal cored board in which a plated layer made of easily solderable metal (such as nickel) is formed over the metal core (such as aluminum) and an electrically insulating layer is formed over the plated layer through an adhesive layer. However, since tile adhesive is of an organic material family and the adhesive force between the plated and electrically insulating layers is not necessarily sufficient, the organic non-conductive layer may separate from the aluminum core in an environment of high temperature and high humidity in the same manner as in the other known constructions described above.
It is believed that a printed wiring board and method of making same that will overcome the above and related disadvantages would constitute a significant advancement in the art.